This invention relates to a method of processing dicalcium phosphate and sodium montmorillonite and more particularly to a method for the changing of sodium montmorillonite to a phosphated montmorillonite in order to produce a thoroughly dispersed stabilized calcium montmorillonite with the crystals of dicalcium phosphate becoming finely subdivided without the application of mechanical grinding action.
The present invention is concerned with hydrated dicalcium phosphate widely available commercially in substantially pure form. Dicalcium phosphate has long been known to be well suited as a polishing agent especially for relatively soft surfaces. It finds application in use as such a polishing agent for dentifrices, silver polishes, lacquer and furniture rubbing compounds and the like. It has also been widely used as a food supplement and in many preparations thereof is used in suspended form in a liquid vehicle so that fine particle size is essential to prevent settling and to maintain a stable suspension to maintain its original state of dispersion.
One problem in using dicalcium phosphate is that it is difficult to create the sufficiently fine particle size necessary for its potential uses and which fine particles hasten any process in which the dicalcium phosphate is to be consumed or utilized from a suspension thereof. Dicalcium phosphate has in some cases been provided so that it completely or substantially passes through a standard 325 mesh sieve. The maximum dimensions of the opening of such a sieve are 44.times.44 microns which is large compared with the desired particle size of 1-3 microns. While it might be possible to reduce the size of this material by specialized grinding methods such as micronizing or steam jet milling or the like, this is an expensive and troublesome expedient and in any case it does not appear to have been resorted to by any commercial manufacturer of dicalcium phosphate.
My U.S. Pat. No. 2,943,982, issued July 5, 1960 discloses a process for simultaneously comminuting and forming a suspension of dicalcium phosphate. In accordance with the process disclosed in that patent, there is formed a suspension of pulverized dicalcium phosphate in water which also contains suspended therein a swelling clay of the montmorillonite group. The suspension is then rapidly brought to a temperature of 200.degree. F. or higher and maintained at such a temperature for a short time, whereupon the preparation is cooled or allowed to cool for subsequent uses.
In many cases, however, it is not desirable to use dicalcium phosphate in an aqueous suspension, and a dispersed solid phase of the substance is preferable.